Android: Ensure gesture navigation shows close indicator correctly

Occasionally the close indicator does not appear when left swipe exits
the app. The condition for exiting (minimizing) app had a bug not
reflecting the tab launch type (when launched from an external app).
This CL rectifies the condition.

Bug: 988546
Change-Id: I8bc93f48400dbf831c998806c7d00de61030b76e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730294Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683790}

chrome/android/java/src/org/chromium/chrome/browser/gesturenav/TabbedActionDelegate.java

@@ -7,6 +7,7 @@ package org.chromium.chrome.browser.gesturenav;
 import android.os.Handler;
 
 import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tab.TabAssociatedApp;
 
 /**
  * Implementation of {@link NavigationHandler#ActionDelegate} that works with
@@ -40,6 +41,8 @@ public class TabbedActionDelegate implements NavigationHandler.ActionDelegate {
 
     @Override
     public boolean willBackExitApp() {
-        return !mTab.canGoBack() && !mTab.getActivity().backShouldCloseTab(mTab);
+        return !mTab.canGoBack()
+                && (!mTab.getActivity().backShouldCloseTab(mTab)
+                        || TabAssociatedApp.isOpenedFromExternalApp(mTab));
     }
 }